Many different types of absorbent products exist that are designed to be worn or otherwise associated with the body for absorbing body fluids. Such absorbent products can include, but are not limited to, diapers, training pants, adult incontinence products, feminine hygiene products, bed liners, bandages, and the like. In some aspects, the absorbent articles contain an outer cover, a liner and an absorbent structure positioned in between the outer cover and the liner. In addition to these foundational functional components of absorbent articles, it is well known in the art to incorporate graphics into such absorbent articles. Graphics may be incorporated into one or more of the functional components. Additionally, the incorporated graphics may serve one or more purposes: aesthetic appeal, toilet-training aid, extent of product usage and physiological state of the wearer of the article. The absorbent structure typically contains superabsorbent particles. Many absorbent articles, especially those sold under the trade name HUGGIES by the Kimberly-Clark Corporation, are so efficient at absorbing liquids that it is sometimes difficult for the wearer or the caregiver to tell whether or not the absorbent article has been insulted with a body fluid, such as urine.
Accordingly, various types of moisture or wetness indicators have been suggested for use in absorbent articles. The wetness indicators can be used for different purposes. For instance, the wetness indicators can be designed to assist parents or attendants by helping them identify a wet diaper condition early on.
Wetness indicators can also be used as a training aid for small children during the toilet training process. For example, wetness indicators can be designed to discourage small children from wetting the absorbent article and to encourage small children to use a toilet like an adult.
Wetness indicators used in the past have included wetness indicator graphics that have been printed on the absorbent article. Absorbent articles having wetness indicator graphics, for instance, are described in U.S. Pat. No. 6,297,424; in U.S. Pat. No. 6,710,221; and in U.S. Patent Application Publication No. 2006/0149197, which are all incorporated herein by reference. Although the above patents have provided great advances in the art, further improvements are still needed.
For instance, prior commercial wetness indicator graphics have been created using moisture-responsive inks that dissolve when wet. The graphics are created using moisture-responsive inks that are printed onto one or more components of the absorbent article. For example, the outer cover component may be formed of a laminate of a breathable, but moisture barrier film and a nonwoven material. Graphics may be formed by printing on one or both sides of the moisture barrier film. The other components of the absorbent article, such as the liner and the absorbent structure, may also be printed with moisture-responsive inks to form the graphics. In some instances, once contacted with urine, the graphics smear and fade indicating that the absorbent article is wet. Unfortunately, however, graphics produced with moisture-responsive inks have been somewhat limited in size, shape, position, line width, color and the like in order to ensure sufficient fading when contacted with urine. The location of the moisture-responsive ink within the construction of the absorbent article impacts the aesthetic performance of the ink. For example, if the moisture-responsive ink is not readily exposed to moisture accumulating in the absorbent structure, the graphic printed with the moisture-responsive ink may only partially change in appearance. In addition to not providing a clear indication of product usage, a partially faded or blurred appearance may detract from the overall appearance of the absorbent article.
Other components of the absorbent article have been found to interfere with the performance (e.g. definition of the graphic fade, completeness of the graphic fade, aesthetic appearance of the graphic fade, etc.) of the moisture-responsive inks. For example, construction adhesive is believed to interfere with the performance of moisture-responsive inks. For example, if construction adhesive is applied over the moisture-responsive ink, the construction adhesive will interfere with the ability of the moisture-responsive ink to change in appearance in response to the presence of moisture. If the moisture-responsive ink is printed on the inward-facing surface of the outer cover component, article components placed between the outer cover component and the absorbent structure may interfere with the performance of the moisture-responsive ink. For example, some absorbent article constructions include a tissue layer or spacer layer between the absorbent structure and the outer cover component. It is believed that the tissue layer/spacer layer may interfere with the performance of the moisture-responsive ink. For example, such layers may interfere with how completely the ink changes in appearance in response to moisture being present. If the moisture-responsive ink “disappears” in response to the presence of moisture, the tissue layer/spacer layer may interfere with the ability of the graphic to fade and disappear in response to moisture. If the moisture-responsive ink changes color in response to the presence of moisture, the tissue layer/spacer layer may interfere with the ability of the graphic to clearly and completely change color in response to moisture.
In some instances, it is desirable for the moisture-responsive ink to change in appearance within a “framed” area of a component of an absorbent article. Examples of absorbent articles having an active graphic with a framing device surrounding the active graphic are described in U.S. patent application Ser. No. 12/852,192 filed on Aug. 6, 2010. When the moisture-responsive ink has to change in appearance within a framed area, it is desirable for the change to be distinctive and to be complete across the entirety of the framed area. Given the general construction of absorbent articles, currently-available moisture-responsive inks and the objective of an aesthetically-appealing article, there remains a need for absorbent articles utilizing moisture-responsive inks to provide dramatic changes in appearance in response to the presence of moisture. There also remains a need to leverage the other components of the absorbent article to improve the performance of the moisture-responsive ink.